Fix link to publish guide in README (#8720)
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## Summary
<!-- What's the purpose of the change? What does it do, and why? -->
The README contains a link to the publish guide
(https://docs.astral.sh/uv/guides/publish.md) that gives an error 404.
When navigating to that page via the side menu, the correct link seems
to be (https://docs.astral.sh/uv/guides/publish/).
## Test Plan
<!-- How was it tested? -->
Documentation change, therefore manual testing by clicking on the link.
